In the times of today, the public is very conscious of the theft of goods from houses and businesses. To a large extent, these thefts are concentrated in electrical appliances of entertainment nature, such as television sets, radios, phonographs, stereo systems, and the like. One feature that all these types of appliances share is that they are connected with a source of power through the usual means of a power cord which plugs into a wall outlet. And, in order to steal the electrical appliance a thief will have to remove the electrical power cord from the wall or pull the power cord out. Thus sensing the removal of available power to an electrical appliance is a means to detect the beginnings of the theft of the appliance.
To this end, many burglar type devices have been devised which sense the physical removal of the electrical plug at the electrical outlet, but none have been devised for detection at the appliance itself and more particularly, having an alarm located on the appliance itself, the alarm also being supplied energy for storage from a source independent of the electrical wall circuit.
For example, burglar type alarm means have already been invented where there is a mchanical interruption of an electrical circuit by sensing the presence of the electrical plug at the wall outlet. In these cases, removal of the electrical plug from the wall socket mechanically interrupts or engages electrical contacts and indication is made at a central control room. This is shown in United States Patents to Cline, U.S. Pat. No. 3,484,775; Sliman, U.S. Pat. No. 3,192,518; and Zeder, U.S. Pat. No. 4,028,691.
Other known burglar type alarm systems dealing with electrical connection at the wall socket are shown in the patents of Manley, et al, U.S. Pat. No. 3,794,989, and Wireman, U.S. Pat. No. 4,075,617, which depend upon electrical connection through the grounding plug of a three wire electrical plug to detect removal of the ac power to the appliance.
While these prior described inventions will detect the removal of the electrical plug from the wall outlet, it is not hard to visualize a situation where the thief may remove the appliance before a person could respond to the alarm, and when the parties responding did arrive, they would find nothing.
Thus it is apparent there is need for an alarm which will attach to the appliance itself, will sound when the appliance is stolen, and which will enable the owner of the appliance, or other parties, to ascertain the location of the appliance during the process of the theft.